Manuscript Summary: The Directorium perpetuum of the monastery of St. Gall, commissioned by Abbot Franz von Gaisberg (1504–1529), consists of seven volumes (Cod. Sang. 533–539). A total of 36 regulae contain the liturgical rules for the Liturgy of the Hours for all possible annual calendars, due to the variable date of Easter. Each rule begins with Epiphany; the rules for the holidays of the Christmas season until the Vigil of Epiphany (which do not depend on the date of Easter) are compiled in Cod. Sang. 539. Cod. Sang. 538 contains the 32nd through 36th rules, for when Easter falls between the 22nd and the 26th of April (reference date in the codex: Septuagesima, February 18th to 22nd). The 36th rule (for the extremely rare case that Easter falls on April 26th) contains only the months of January and February, since years with this date for Easter are always leap years, and the previous rule therefore covers all moveable feasts after the last day of February. The illumination of the manuscript is by an assistant to Nikolaus Bertschi from Rorschach: p. 1, 57, 115, 173 and 235 contain initials in opaque colors with scrolls or richly decorated borders. This volume was written by the St. Gall cathedral organist Fridolin Sicher. (sno)